For the next thirty days they quarried the shale and slid samples down the ridge to the trail where they were loaded onto pack horses and made their way to the CPR station at Field. Eventually some 65 000 specimens on 30 000 slabs of rock were delivered to the Smithsonian Institute.

Although Dr. Walcott spent a considerable amount of time at the Burgess Shale quarry on what became known as Fossil Ridge, he travelled widely in other areas of the Canadian Rockies. Some of his numerous scientific publications feature spectacular panoramic photographs of the mountains taken from high passes or high on mountain slopes.

After his death in 1927, Walcott’s samples, photographs, and notes remained in storage until a new generation of palaeontologists became interested in them in the late 1960’s.

The key to the remarkable preservation of the animals of the Burgess Shale was the Cathedral Escarpment, a 150 metre high submarine cliff which existed in the seas which covered this area 515 million years ago during the Cambrian era. The dozen or so Burgess Shale fossil discoveries lie below the escarpment. Creatures of the era lived in the shallow water above the escarpment but during major storms great quantities of mud and creatures were swept over the cliff to the bottom far below. At this level there was no light, little dissolved oxygen, and virtually no life. The fossils were thus left undisturbed by scavanging animals and other decomposers of the day.

A second critical factor to the preservation of the soft body parts which make these fossils so special was that the carcasses were coated with a thin film of clay which was forced into all parts of the animal’s body during the tumble down the escarpment. This covering inhibited the decomposition by bacteria.

An important outcome of the more recent study of the Burgess Shale fossils was the discovery that Walcott had misinterpreted many of them, presuming that the fossil imprints were two dimensional and could be analyzed by studying the imprint on a single layer of shale. Recent study shows that the creatures were buried in various orientations and that their impressions were preserved, and had to be interpreted in, three dimensions. This has led to the revision of much of Dr. Walcott’s work and the discovery of the tremendous extent and variation of life in the Cambrian Seas which once covered this area of the Rockies.

Many of the fossils of the Burgess Shale are from animals that are unique and not related to any others known to have lived before or since. A remarkable diversity of life with numerous phyla and classes of animals is seen to have existed, a diversity which thrived during the Cambrian period but then was reduced dramatically. A number of these life forms existed only during the Cambrian and did not evolve into subsequent life forms as time unfolded.

The recently identified animals include Anomalocaris which, with a length of fifty centimetres, is huge by Cambrian standards. A predator, it had spiked feeding arms which grabbed its prey and then fed it into its circular mouth. Another, Opabinia regalis, was a bizarre, five to ten centimetre long beast with five eyes and a mouth on the end of a long tube. It was propelled by paddle like legs which allowed the animal to hover near the bottom of the sea floor.

The area below the top of Fossil Ridge has been deemed to be of such significance that it was declared a World Heritage Site by UNESCO, the United Nations Educational, Scientific and Cultural Organization.